This invention pertains to a control system for a two-cycle internal combustion engine having a function of changing a rotational direction of the two-cycle internal combustion engine.
There has been used a small-sized two-cycle internal combustion engine as a power source for a vehicle such as a scooter, a snowmobile, a buggy car and so on for which a simplification is important and there has been generally used a centrifugal clutch type continuously variable transmission as a power transmission gear to transmit an output of the internal combustion engine to a drive wheel. There has been the continuously variable transmission having a backup gear assembled therein because small size, lightness, inexpensiveness and simple manipulation are important for that kind of vehicle.
Since the vehicle having no backup gear assembled therein cannot move back, the whole vehicle has to be lifted up in order to change the traveling direction in a narrow place, which causes the manipulation to be poorer.
The U.S. Pat. No. 5,036,802 discloses a control system for an internal combustion engine adapted to change a traveling direction of a vehicle by changing a rotational direction of the two-cycle internal combustion engine in consideration of the characteristic in which the two-cycle internal combustion engine can rotate in either of forward and reverse directions.
The apparatus illustrated in the U.S. Pat. No. 5,036,802 is adapted to firstly fail to ignite the two-cycle internal combustion engine when a reversion command is applied to the engine to lower the rotational speed thereof Thereafter, as the revolution rate of the engine is so sufficiently lowered as to get fully lower inertia of a piston, an ignition position of the engine (a rotation angle position of a rotary shaft of the engine when it is ignited) is advanced to an over-advanced position (a position where the ignition position of the engine is more advanced than the proper maximum advance position on a steady-state operation of the engine). As the engine is ignited at the over-advance position in the condition of the engine having the fully lower inertia, the piston moving toward the top dead center is forced backward so that the engine rotates in the reverse direction. In this manner, after the reversion of the rotational direction of the engine is confirmed, the engine can be operated while the rotational direction is kept reversed by igniting the engine at the proper ignition position in that rotational direction.
In the internal combustion engine control system illustrated in the U.S. Pat. No. 5,036,802, the four-pole magneto generator is used which is mounted on the internal combustion engine. The rotational direction of the engine is judged from the phase of positive or negative half waveform of a two cycle AC voltage generated by the magneto generator whenever it rotates one revolution and as the reversion of the rotational direction of the engine is judged, the engine is adapted to be operated while the rotational direction is kept reversed by igniting the engine at the proper ignition position in that rotational direction.
However, with the system constructed in such a manner, since the rotational direction of the engine cannot be judged unless the four-pole magneto generator is used, the magneto generator having more poles cannot be used for improving the output thereof.
There has been proposed a control system for an internal combustion engine control system which comprises two signal generators generating signals in synchronization with the rotation of the engine while they are displaced from each other in the rotational direction and detects the rotational direction of the engine from the phase relation of the signals generated from the signal generators as disclosed in U.S. Pat. No. 5,794,574.
Such a control system as detects the rotational direction of the engine from the signals generated by the signal generators separately provided from the magneto generator requires no four-pole magneto generator and therefore can have the multi-pole magneto generator, which enables more electric power to be taken out of the generator.
However, with the rotational direction of the engine adapted to be judged by using only the output of the signal generators, since the two signal generators are required, the construction of the engine cannot be avoided from being complicated.
Accordingly, it is a principal object of the invention to provide an internal combustion engine control system adapted to detect a rotational direction of an internal combustion engine by using only one signal generator so that the reversion of the rotational direction of the engine can be controlled without any complicated construction of the engine.
In accordance with the present invention, there is provided a control system for an internal combustion engine comprising a rotational direction change-over switch to be operated when a rotational direction of a two-cycle internal combustion engine should be reversed and a microcomputer to perform a speed reduction step to reduce the rotational speed of the internal combustion engine when the rotational direction change-over switch is operated, an over-advance angle control step to advance an ignition position of the internal combustion engine to an over-advance position when the rotational speed is reduced to less than a set value, a rotational direction judgment step to judge the rotational direction to confirm whether the rotational direction of the internal combustion engine is reversed by the over-advance angle of the ignition position and a reversion initial ignition step to ignite the internal combustion engine at the low speed ignition position in the condition of reversing the rotational direction when the reversion of the rotational direction is confirmed, the control system further comprising an AC magneto generator constructed to generate an AC output voltage of 2n cycles (xe2x80x9cnxe2x80x9d is an integral number of more than 1) per revolution of the internal combustion engine with a phase of the AC output voltage being set so that either of zero cross points of the AC output voltage corresponds to the low speed ignition position on the reverse rotation of the internal combustion engine and a signal generator constructed to generate a pulse signal of one of the polarities and a pulse signal of other polarity in synchronization with the rotation of the internal combustion engine with generation positions of the pulse signals being set so that the pulse signals of one polarity and of other polarity are generated at the low speed ignition position on the forward direction of the internal combustion engine and at the position advanced relative to the low speed ignition position, respectively and so that the polarity of one half wave of the AC output voltage of the magneto generator when the pulse signal of one polarity is generated is identical to the polarity of one half wave of the AC output voltage of the magneto generator when the pulse signal of other polarity is generated.
With the magneto generator and the signal generator provided in this manner, the polarities of the half waves of the output voltage of the magneto generator when the signal generator generates each pulse signal are different from each other relative to the forward rotation and the reverse rotation of the engine. This invention judges the rotational direction of the engine by utilizing this difference of polarity. More particularly, the microcomputer is programmed to judge the rotational direction of the internal combustion engine from the polarity of the half wave of the AC output voltage of the magneto generator when the signal generator generates the pulse signal of either polarity.
In a preferred embodiment of the invention, the microcomputer accomplishes rotational direction judgment means to judge the rotational direction of the engine, ignition position arithmetical operation means to arithmetically operate the ignition position of the internal combustion engine, steady-state operation ignition control means to control the ignition of the internal combustion engine on a steady-state operation and rotational direction change-over means to control the engine when the rotational direction of the engine should be reversed.
The rotational direction judgment means is so constructed as to judge the rotational direction of the internal combustion engine from the polarity of the half wave of the AC output voltage when the signal generator generates the pulse signal of either polarity.
The ignition position arithmetical operation means arithmetically operates the ignition positions of the internal combustion engine when it rotates forwardly and reversely at a set value or more than of the rotational speed, respectively. The ignition position is arithmetically operated in the form of time (the number of clock pulses counted by a timer) measured by the timer provided in the microcomputer while the rotary shaft of the engine rotates from the specific rotation angle position (the position where the measurement starts) to the ignition position. The positions where the measurement of the ignition position starts vary on the forward rotation and the reverse rotation of the engine.
The steady-state operation ignition control means is so constructed as to ignite the internal combustion engine when the ignition position arithmetically operated by the ignition position arithmetical operation means is detected in the condition where the internal combustion engine rotates forwardly and reversely at the set value or more than of the rotational speed, to ignite the internal combustion engine when the pulse signal of one polarity generated by the signal generator is detected in the condition where the internal combustion engine forwardly rotates at less than the set value of the rotational speed and to ignite the internal combustion engine when the zero cross point of the AC output voltage corresponding to the low speed ignition position of the reverse rotation is detected in the condition where the internal combustion engine reversely rotates at less than the set value of the rotational speed.
The rotational direction change-over means includes speed reduction means to reduce the rotational speed of the internal combustion engine when the rotational direction change-over switch is operated, ignition position over-advance means to ignite the internal combustion engine at an advance angle position necessary for reversing the rotational direction of the internal combustion engine when the rotational speed of the engine is reduced to the set value or less than and reversion initial ignition control means to ignite the internal combustion engine at a reversion initial ignition position suitable for a first ignition position after the rotational direction is reversed when the reversion of the rotational direction of the internal combustion engine is judged by the rotational direction judgment means.
The rotational direction change-over control means is so constructed to decide the reversion initial ignition position when the rotational direction of the internal combustion engine is changed from the forward direction to the reverse direction on the rotation angle position information obtained from the zero cross points of the AC output voltage of the magneto generator and to set the reversion initial ignition position when the rotational direction of the internal combustion engine is changed from the reverse direction to the forward direction, at a position where the signal generator generates the pulse signal of one polarity.
It should be noted that the positions where the measurement of the ignition position arithmetically operated when the engine rotates in the forward and reverse directions starts are set at the ones more advanced than the over-advance positions when the engine rotates in the forward and reverse directions, respectively, in order to enable the over-advance of the ignition position.
In this manner, the system of the invention can judge the rotational direction of the engine from the polarity of the half wave of the output voltage of the magneto generator when the signal generator generates the output pulses. This can prevent the construction of the engine from being complicated because the rotational direction of the engine can be judged by using only one signal generator.
In the invention, the information on the position where the measurement of the ignition position starts may be obtained from either the output of the signal generator or the output of the AC magneto generator.
More particularly, the steady-state operation ignition control means may be so constructed to start the measurement of the ignition position arithmetically operated by the ignition position arithmetical operation means when the signal generator detects the pulse signal of other polarity during the forward rotation of the internal combustion engine to ignite the internal combustion engine after the measurement of the ignition position ends and to start the measurement of the arithmetically operated ignition position when the signal generator detects the pulse signal of one polarity during the reverse rotation of the internal combustion engine to ignite the internal combustion engine after the measurement of the ignition position ends. Alternatively, it may be so constructed to start the measurement of the ignition position arithmetically operated by the ignition position arithmetical operation means when the specific zero cross point of the AC output voltage is detected to ignite the internal combustion engine after the measurement of the ignition position ends.
Otherwise, the steady-state operation ignition control means may be so constructed to start the measurement of the ignition position arithmetically operated by the ignition position arithmetical operation means when the pulse signal of other polarity generated by the signal generator is detected during the forward rotation of the internal combustion engine to ignite it after the measurement of the ignition position ends and to start the measurement of the ignition position arithmetically operated by the ignition position arithmetical operation means when the specific zero cross point of the AC output voltage is detected during the reverse rotation of the internal combustion engine to ignite it after the measurement of the ignition position ends.
The speed reduction control means may comprise means to stop an operation of an ignition system to misfire it, for instance.
In order to stop the operation of the ignition system, an electric power source may be made ineffective which supplies an igniting energy to the ignition system, a portion of the circuit elements of the ignition system may be shorted or the ignition command signal stops being supplied to the ignition system, for example.